Ringing Ears / Tinnitus

A gut-brain-ear axis

Researchers have found a direct genetic link between gut bacteria and tinnitus risk, one of the stronger findings in this whole area of research. Tinnitus, a ringing or buzzing sound with no external source, has no cure. A large study of over 400 gut microbiome features and a Finnish tinnitus database found that higher levels of one bacterium, Parabacteroides distasonis, were linked to lower tinnitus risk, a 16% reduction, while higher levels of another, Eggerthella, were linked to higher risk.

Source: PMC, Effects of Gut Microbiome on Tinnitus: A Mendelian Randomization Study

What is actually different in the gut

A separate study compared the gut bacteria of 70 people with chronic tinnitus against 30 healthy volunteers. The tinnitus group had noticeably lower bacterial diversity overall, along with a higher ratio of Firmicutes to Bacteroidetes, two of the largest bacterial groups in the gut, a shift researchers have linked to inflammation in other conditions too. Two specific, usually low-level bacteria, Aeromonas and Acinetobacter, were more common in the tinnitus group, while helpful bacteria from the Lactobacillus family were less common. The tinnitus group's blood also showed a distinct pattern of metabolites, the chemical compounds these bacteria produce. The researchers introduced the term "gut-brain-ear axis" to describe how gut bacteria may influence tinnitus by changing the body's metabolic profile.

A review of 22 studies found that gut bacteria disruption affects levels of neurotransmitters including GABA and serotonin, and increases inflammatory signalling molecules in the brain, patterns also seen in people with tinnitus. This does not prove gut bacteria cause tinnitus, but it gives researchers a specific, testable mechanism to investigate.

Source: Microbiology Spectrum, Characteristic alterations of gut microbiota and serum metabolites in patients with chronic tinnitus

Source: PubMed, The Role of Gut Dysbiosis in the Pathophysiology of Tinnitus: A Literature Review

The same protective bacterium shows up in animal studies too

Researchers studying mice bred to be more vulnerable to noise-induced tinnitus found their gut bacteria shifted in a specific way after noise exposure. Several harmful bacteria increased, while one bacterium fell: Parabacteroides distasonis, the exact same bacterium the earlier genetic study found protective against tinnitus in people. Seeing the same specific bacterium turn up as protective in two completely different kinds of study, human genetics and mouse experiments, makes this a more convincing finding than either study would be alone.

Researchers have also traced part of the mechanism. In mice with noise-induced hearing loss, a specific inflammatory signal, TNF-α, was found raised in the hearing-related part of the brain, alongside activated immune cells there. When researchers blocked TNF-α, or removed the gene for it entirely, the mice stopped showing tinnitus-like behaviour. Separately, giving rats a specific probiotic strain, Lactobacillus rhamnosus GG, reduced noise-related inflammation and memory problems, partly by increasing short-chain fatty acids and strengthening the gut barrier.

Source: Scientific Reports, Nrf2 deficiency enhances oxidative stress and promotes susceptibility to tinnitus in mice

Source: Lactobacillus rhamnosus GG ameliorates noise-induced cognitive deficits and systemic inflammation in rats

What this means for you

Tinnitus should be assessed by a doctor, since it can occasionally signal an underlying condition, such as earwax blockage or a specific ear or blood vessel problem, that needs its own treatment. Existing therapies, including sound therapy and cognitive behavioural therapy, remain the main tools with an evidence base, and neither replaces the other. Supporting the gut microbiome through a varied, plant-rich diet is a reasonable, low-risk addition given the genuine biological link researchers have found. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.